Sorry I didn't have time to reply to this thread earlier, hope this isn't too late. I've done a DipABRSM on clarinet, and I was going to take ATCL Treble Recorder (although I didn't in the end as I had too much to do with A levels at the time) so I do have some experience of these exams.
Programme notes: Start of with the basic information about the piece, when it was composed and where, first performance etc. If it's possible, find out who it was originally written for (which performer), as knowing this can help you decide how to interpret the piece, and this type of information is usually interesting for the reader too. It's also good to put the piece in context - did the composer write many pieces for the flute, what else was he writing at the time, and any social factors that might be relevant. Try to condense this down to a few sentences so you aren't filling up your word count on background info. Then move on to an overview/analysis of the piece. You could comment on movements, structure, tonality, harmony etc and then balance this with less analytical language by commenting on the mood, tone or character of the piece. I think they want you to write in an accessible way as though for a general audience (This is true for ABRSM anyway, might be worth checking up for Trinity). You should focus on this part mainly, but it doesn't need to be too long - I'm not sure what the word count is but it should be just enough to give the general character of the piece.
I don't think you'd need to verbally introduce your programme verbally, handing over the programme notes should be fine.
I'm sorry I don't have any experience of the marking as I've never taken the exam.
I don't know any of the pieces you're playing as I'm not a flautist but in terns of the composers you have chosen you look to have a nicely balanced programme with a good range of composers. When you time your pieces, it might be worth running the programme through as though you were actually doing the exam, so setting the timer going, putting your music on the stand, tuning up and retuning if you like between movements, having a breather between pieces just to give you an idea of whether another piece is needed. Hope this helps a bit!